Optical testing stand



Sept. 1, 1936.

war s mm:

F. G. WILLIAMS 2,052,591

OPTICAL TESTING STAND Filed Oct. 16, 1934 2 Sheets-Sheet 1 lNVENTOR ATORNEY Sept; 1936- F. G. WILLIAMS OPTICAL TESTING-STAND Filed Oct. 16,1934 '2 Sheets-Sheet 2 INVENTOR E5. Williams ATTORNEY Patented Sept. 1,1936 UNITED ,STATES PATENT oFFicE 1 Granted under the act .or lllarch 3,1883, as amended April 30, 1923; 370 0. G. 757) This invention relatesto apparatus for testing optical instruments of the octant or sextanttype and has-forits object to provide means for determining the error inthe indication of the instrument for given angular movements of theoptical axis of the instrument andalso to determine the errorsintroduced by tilting the instrument from its normal plane and those dueto the use of shade glasses.

In the drawings: a s

"Fig. 1 is perspective view of the principal operating parts of myinvention; I

Fig. -2 is a perspective view-of the entire stand taken substantially 90from Fig. 1; 1

Fig. 3 represents'an artificial sun used in testing with shade glasses.I T

It is well known that the readings obtained from instruments ofthe'octant and sextant type are not absolutely accurate and thedeviation from accuracy is different for various changes in the angularposition of the optical axis. Further, errors are introduced it theinstrument is not held'in a certain plane and other errors are causedwhen'shade glasses are employed to diminish the intensity of the light.-The present invention determines accurately the presence and magnitudeofsuch-errors- I.

Asis shown infFig. 2, the stand comprises a heavy pedestalhavingan uppersurrac'e 5,---that is made accurately horizontal by means of levelingscrews 6,- bubble-levels 1 and 8 being pro-'- vided to show when thesurface 5 is horizontal. A rigid arm 9 is firinly secured to the-base 4against surface 5, this-arm having a horizontal portion l and an arcuateportion l I.

A plurality of collimators 42', are secured against one side face of thearcuate portion ll of arm 9 over an angularextent of one quadrant, theoptical axes 'oi the coll-imators being preferably uniformly angula'rlyspaced and all-passing through a -common point at the center of thequadrant defined by the collimatorsi Each collimator 4-2 is providedwith =-an electric light bulb and all the bulbs are connected in seriesby the wire 13,1. pilot light being also connected in series with thecollimator lights to indicate when all of the latter are lighted.Secured to the tube of each collimator I2 is a level l5 which isaccurately positioned with respect to the optical axis of the collimatorand at such angle to that axis that when the bubble level is in itscentral position the axis of the collimator has the requiredinclination.

Mounted upon the horizontal portion ID of arm 9, is a universaltraversing mechanism such as iswell known on'machine tools. It comprisesa vertically movable slide I6, operablecby means of hand wheel I! andbevel gears l8 which drive a screw engaged with slide IS in a mannerwell which is formed into two arms 25 at its upper end. The member ismounted on the slide 2.1 to be rotatable about its vertical axis bymeans of handwheel 26, worm 2'! and gear (not shown) on the member 25meshed with worm 21. A journal28 is mounted in the arms 25 to beswingable about gudgeons 29, the tilting thereof being efiectedzby crank30 and the inclination of the'longitudinal axis thereof to thehorizontal being indicated by pointer 3i which moves over scale 32. Aplate 33 and concentric spider 34 are fixed to shaft 35 which isrotatable in journal 28, the face 36 of the spider 34 being calibratedin'units of arc. A cup 31 is mounted on the free face of plate 33, theangular position of the cup being susceptible of micrometer adjustmentby 'means of the screw 38 which acts upon a radial arm which may beengaged by means of a clutch (not shown) to the shaft 35 and which inturn is connected to the cup 3'1. Screws 39 are threaded into and extendthrough the wall of cup 31 to contact the instrument to be tested whichis mounted in cup 31, the perimeter of the free edge of cup 31 beingvariable by means of clamp screw 40.

Micrometer reading microscopes 41 are mounted in arms-42 .carried byjournal 2.8 and are disposed to readthe calibrations on face 36 ofspider rim .31, the lights 43 being positioned to project abeampf lightupon the face 36 adjacent each of the microscopes 4i.

The collimator lights are controlled by a switch aotuatable by chain 44,the artificial sun, hereinafter described, being controlled by a switchoperated by chain 45 and the lights 43 by switch 46.

The artificial sun 41, shown in Fig. 3, is constructed to provide aluminous area that substantially corresponds, in the angle interceptedthereby, to the natural sun and is used for determining the errors inreading an octant introhorizontally extending collimator in the bottomof the series and with the indicated reading on the instrument at zero.

ersing any of the slides l6, l9 and 2| or by rotating the tubular member25 and veryfine adjust- Y 'ment is secured through the screw"38 .and themechanism cooperating therewith. Afterhaving effected such alignment theplate 33 is ro-' tated to bring the optical axis of the instrument beingtested into alignment with the beam of light from the nexthighercollimatontheFindicated angle being read on the instrument andthe' 7 accuracy thereof being checked by noting the angular movement ofspider 34 and since means are provided for taking micrometerrreadings ofthe rotational movement of 'the spider a very accurate check can bemade, of the *indication'of the instrumentunder test. This process isrepeated, bringing the optical axis of the o'ctant successively intoalignment with' the optical axes of the collimators through the entireseries from zero to 90. i

The error introduced by agiven lateral dis-' placement of the octantfrom a vertical plane, for each interval of vertical angle is determinedby rotating crank 30 to tilt the journal 28 and so move the instrumentsecured in cup 31 a known angular magnitude out of a vertical positionand then bringing the optical axis of the instrument into alignment withthe collimators as above described.

The invention described herein may be manue factured and used by or for'theGovernment of said collimators being substantially uniformlyangularly spaced from the axes of thecollimators adjacent thereto, andall said axes passing through a common point, a rotatable member mountedwith its axis of rotation normally pass ing through said common pointtransversely to said optical axes, means to fix to said member aninstrument to be tested so that the. optical axis thereof may be broughtselectively into coincidence with the optical axes 'of the collimators,and means tomeasure the angles throughiwhich said .instrument'isrotatedinsecuring such coincidence of the axes. r

Any adjustments necessary to secure such alignment are made by trav---with its axis, of rotation normally passing through 2. A stand fortesting optical angle-measuring instruments, comprising a base having anaccurately horizontal upper surface, a rigid arcuate arm secured againstsaid surface, said arm hav- 7 ing a vertically extending face, aplurality' of' collimators secured against said face in a circular arcof one quadrant, the optical axis of each of said 'col'l'imators being"substantially uniformly angularly spaced from the 'axes ofthe-collimators acommon point, a rotatable member mounted said cominonpoint transversely to said optical axes,-'meansto fix 'to said member aninstrument to be tested so thatthe optical axis thereof may be broughtse'lctivelyinto coincidence with the opticalaxes of the collimators,means to tilt said member about an axis perpendicular to the axis"of'rotation of said member, and means to measure'the angles throughwhich said member is rotated to secure, such coincidence of the-axes; 3Astand for testing optical angle-measuring instruments, ,.comprisingaplurality of, collimators optical axes of the collimators, and means "tomeasure the angular movementof such instrument in securingsuchcoincidence of the axes 4. A stand for testingopticalangle-measuring 7 instruments, comprising means toprovide a plurality of beams of parallel light,- the axes ofsaid beams being inpredetermined angular relation and passing througha common point,means-to support adjacent said common point an instrument to be tested,in position to have its optical axisbrought selectively into coincidencewith the axes of said'beams, means to tilt said supporting meanstransversely tothe axesof said beams, and means to measure, t ang thr uh whi h the instrument being tested is moved in securing thesaid-coincidence of "said axes. H I

5. A stand for testing optical angle-measuring instruments, comprisingmeans to provide aaplue rality of beams of parallel light, the axes ofsaid beams being in predetermined-angular relation and passingthroughacommon point, means for mounting adjacent said common pointaninstrument to be tested, in position tohave itsoptical axis broughtselectively into coincidencewith the axes, ofs fid a me ns f me s ri a crately vertical angles through which the optical axis. of saidinstrument is ;rqtated by. movement of said mounting means, means ,fortilting said mounting. means transverselyto the said vertical movementof the said optical axis, and means for asur th an le of su h t t, wh rey the er-v rors in the indicationt of .verticalangles, intro; ducedinto-the readings of saidiinstrument by such tiltin through. any givenangle may be ascertained.

